1. Field of the Invention
The present invention relates to an antenna device and, more particularly, to an antenna device for use in a mobile telephone operating within a frequency band from 800 MHz-960 MHz.
2. Related Art of the Invention
A mounting position for a mobile telephone antenna on a car is selected from a variety of positions considering available installation points on a car body and assuring clear vision of a driver. For example, rooftop, roofside, and trunk grid are selected as a mounting position. A wire-like antenna to be mounted there is typically a monopole antenna as shown in FIG. 12. The monopole antenna 50 is an antenna element 52 of a 1/4-wave length (1/4 .lambda.) mounted on a ground plate 51 such as a roof of a car. The antenna element 52 has one end connected to a feeder section 53 connected to a power source V with the other end being an open end 54.
In case of the above conventional monopole antenna, the antenna element of 1/4-wave length is 8 cm-9 cm in a mobile telephone operating in a frequency range of 810 MHz-956 MHz, for example. With such an antenna, the following problems are raised: (1) the antenna degrades the aesthetic appearance of the car; (2) the antenna results in an increased air resistance of the car body; (3) the mounting positions available are limited; and (4) the types of car permitting mounting are limited.